1. Field
This invention relates to an improvement in a process for preparing acylic amines and the improvement resides in the vapor phase hydrogenation of the corresponding acyclic nitriles to form the amines.
2. Background of the Invention
U.S. Pat. No. 3,117,162 and U.S. Pat. No. 3,177,258 show hydrogenation reactions using a ruthenium-containing catalyst often combined with platinum, palladium or rhodium and the hydrogenation of nitriles (162) to form the corresponding amines. The 162 patent discloses that various nitriles, such as propionitrile and benzonitrile, can be hydrogenated at temperatures from 0.degree.-400.degree. C. in liquid phase and temperatures of 100.degree.-400.degree. C. with space velocities from 0.1-50 volumes vapor per volume of catalyst per hour under vapor phase conditions. The example shows that a high level of di-n-propylamine can be achieved by the liquid phase hydrogenation using rhodium on a carbon catalyst. Palladium on carbon resulted in a high concentration of the tertiary amine. As the temperature is increased, e.g. to 150.degree. C., randomization of the amines product slate, particularly with rhodium, results.
German Patent No. 79,021 discloses a process for the continuous production of various ethylamines by hydrogenating acetonitrile over a fixed bed containing nickel or chromium catalyst. Hydrogenation is carried out at pressures from 5-230 atmospheres at temperatures between 100.degree.-180.degree. C. Selectivity to specific amines is achieved by operating a separation unit at temperatures from -33.degree. to 50.degree. C. and recycling the balance. Diethylamine in 91% yield was obtained at a separator temperature of 2.degree. C. Acetonitrile was converted to monoethylamine in an 88% yield using a separator temperature of 29.degree. C.
U.S. Pat. No. 3,468,953 discloses a process for preparing methylamines by the gas phase hydrogenation of hydrocyanic acid. The hydrogenation is carried out at a temperature from about 150.degree.-300.degree. C. in the presence of platinum metals preferably disposed upon diatomaceous earth or kaolin.
U.S. Pat. No. 3,427,356 discloses a process for preparing propylenediamines, particularly the primary amine, by hydrogenating aminopropionitriles. The hydrogenation is carried out in the presence of ammonia at temperatures below 200.degree. C. using cobalt or nickel as the catalyst, the catalyst being promoted with a small amount of manganese.
U.S. Pat. No. 3,166,596 discloses a process for preparing a mixture of triethylenediamine and n-propylamine by reacting a mixture of acrylonitrile, hydrogen and aqueous ammonia under mild conditions in the presence of a hydrogenation catalyst. The reaction is carried out at a temperature from 50.degree.-350.degree. C. with pressures of from 15 to 200 atmospheres. Ratios of ammonia to acrylonitrile are approximately 5-40:1 on a molar basis with the balance being water. The product slate is sensitive to water, the higher the concentration of water the higher the concentration of n-propylamine.
U.S. Pat. No. 3,501,528 discloses the liquid phase hydrogenation of higher aliphatic or cycloaliphatic, nitriles having from 8 to 24 carbon atoms at temperatures of 220.degree.-400.degree. C. and pressures of from 50-400 atmospheres with excess hydrogen. Conventional hydrogenation catalysts, e.g. nickel, platinum, palladium, and the like are used.
Belgian Patent No. 860,470 discloses a liquid phase batch process for producing dipropylamine by the catalytic hydrogenation of acrylonitrile at a temperature of from 50.degree.-130.degree. C., and hydrogen pressure of from 1-60 bars. Long reaction times are utilized. A catalyst composed of rhodium on an inert support, e.g. alumina, silica and like is used. Yields of 65 to 83% dipropylamine at reaction temperatures from 75.degree.-100.degree. C. and pressures of 24 to 50 atmospheres are reported.